where \(G(Q_*)\)  accounts for the effect of the coupling of the inflaton
and radiation fluctuations. Some explicit forms for \(G(Q_*)\)  have
been given in the literature, depending on the form of the dissipation
coefficient in
WI [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}.
In the next section we will give results for \(G(Q_*)\)  in the DBIWI
case for some of the most representative dissipation coefficient forms
used in the recent literature and we will also explicitly see how a
\(c_s<1\)  effectively suppresses the effects of a growing \(Q_*\)  in the
amplitude of the scalar power spectrum. But before going into that
analysis, let us also derive some useful results concerning the
spectral tilt in DBIWI.
